When a computer is connected to a public network, such as the Internet, the computer is vulnerable to attack and compromise from other computers on the network. In contrast, if the same computer is connected to a private network, such as a corporate local area network (LAN), the security risks are much fewer, and features like file and printer sharing are common. Therefore, firewall software has been developed to protect the computer and such software is configurable by the user to determine the level of security desired.
In many cases, the computer may be connected to different networks at different times. For example, a notebook computer that is connected to a corporate LAN when the user is in the office may be connected to a public network when the user is working at home or traveling. The security configuration for the computer when it is used in the office would allow most all network traffic to and from the LAN because the LAN is a trusted network. On the other hand, when the computer is connected to a public network, the security configuration should be changed to prevent almost all unsolicited traffic because the public network is untrusted.
Using prior art firewall software, the user must manually re-configure the security settings when changing network connections, posing significant risks and challenges in protecting the computer. If the user attempts to connect to a trusted network with the firewall configured for an untrusted network, the user probably cannot log into the corporate LAN because it is likely that some of the protocols allowed on the LAN are prohibited on the untrusted network. More critically, if the firewall software is configured for a trusted network when the user connects the computer notebook to an untrusted network, the computer is now much less protected from attack.